Do you remember your first bout with the flu? Probably not, since it happened decades ago.
But, your body remembers very well, at least according to a new study from the University of Arizona. The study showed the first flu virus your body encounters as a young child indicates how well your body will protect itself against the flu in the future.
This research is important, because recent flu seasons have been more dangerous than previous seasons.
Due to a mutated H3N2 strain of the flu, the 2017-18 season was the worst of the decade. By the end of that flu season, over 80,000 people in the United States died from the virus.
Michael Worobey, is the co-author of the study. Worobey, the head of the Department of Ecology and Evolutionary Biology at the University of Arizona, looked at this trend.
It wasn’t until 2016 when Worobey and his co-authors of the new study presented a paper for the journal Science. It was this paper that showed that past exposure determines an individual’s response to the flu virus.
Importance of Your First Flu Infection
According to the University of Arizona, “for decades, scientists and healthcare professionals were vexed by the fact that the same strain of the flu virus affects people to various degrees of severity.”
The reason for this has to do with which strain of flu a person first came into contact with as a child.
For example, a child who first came in contact with a strain of H1N1 flu will fight off H1N1 flu better in the future than if they were to catch the H3N2 flu virus. Additionally, if that same child did catch the H3N2 strain, it would affect worse than if they caught the H1N1 strain again.
Not only do the results explain why some fend off a flu strain better than others, but also resolves a long-held belief about the flu. As both A strains of influenza, H1N1 and H3N2 strains come from the same group. For years, researchers believed this meant exposure to one strain would help the body fight off the other strain.
But, the results show that isn’t the case.
Our immune systems often find it difficult to recognize and fight against closely related strains of the flu. Researchers find this perplexing thanks to the immune system’s memory.
Katelyn Gostic, lead author of the study and doctoral student at the University of California, Los Angeles, explained the issue. The immune memory can “recognize and defend against distantly related, genetic third cousins of the strains we saw as children.”
Although the influenza strains are closely related, the body responds to them differently. The study did offer some other details about this confusing result.
What Else Affects Our Ability to Fight the Flu?
Not only is the initial flu strain important, but the order in which you encounter the strains is crucial as well.
“Whichever subtype our immune system sees first lays down an imprint that protects us especially well against strains of the same subtype,” said Worobey. He explained that the “investment of fighting the last war” prevents the immune system from a similar response to a different virus later.
Still lacking a lot of answers, researchers are looking into the importance of the first flu strain. They are focusing on molecular cases of this effect for more information. They hope future findings will help with this problem and predict age groups that might be severely affected during flu seasons.
“We need a vaccine that targets the deficits on an individualized level. Our work has clearly shown that the first virus we had can have a profound long-term effect,” said Worobey. “The bad side of that is that our immune system seems to be locked into fighting just one half of flu genetic diversity, and we need to find ways of breaking that.”
Written for Passport Health by Elle Johnson. Elle Johnson is a senior multimedia journalism student at the University of South Carolina. Johnson is graduating with a bachelor’s degree in December and is a freelance writer in her free time.